The present invention is directed to a novel, hydrophilic, ampholytic polymer. Hydrophilic polymers readily associate with, have an affinity for, and dissolve in water. Ampholytic polymer(s), or polyampholyte(s), are polymer(s) having both cationic and anionic groups. The polymers of the present invention have utility as rheology modifiers in cationic and low pH (acidic) systems, as bioadhesives, as agents in the removal of bile salts and for enzyme inhibition, and as phosphate binding agents.
Ampholytic polymers are known. For example, U.S. Pat. Nos. 5,286,827; 5,216,098; 5,130,391; 5,116,921; and 5,075,399 teach superabsorbent crosslinked ampholytic ion pair copolymers, which are in powder form for incorporation into baby diapers. The ampholytic nature of the polymer facilitates the absorption of urine.
Polymers which are used as rheology modifiers or thickeners include non-ionic, cationic, anionic, and associative type thickeners. Non-ionic polymers include, for example, naturally occurring and chemically modified gums. Cationic polymers tend to be nonionic polymers, such as the natural gums which have been quaternized to make them compatible with cationic systems, although synthetic polymers are known, such as U.S. Pat. Nos 5,603,926 (Matsumoto et al) and 5,608,021(Uchiyama et al), which teach polymers from acrylic monomers having amino groups, and U.S. Pat. No. 5,321,110 (J. S. Shih), which teaches a vinyl pyrrolidone based polymer that includes an acrylic monomer having an amino group, which is quaternized to make it cationic. Anionic polymers, or polyelectrolytes include polycarboxylic acids, such as polyacrylic acid and the like. Associative polymer thickeners include hydrophobically-modified variations of non-ionic and ionic polymers, which function by xe2x80x9cself-associationxe2x80x9d when dissolved in aqueous systems.
Unfortunately, however, the aforementioned conventional water-soluble polymers suffer from many serious deficiencies or limitations in actual use. For example, polymers are often added to personal care, medical, pharmaceutical, and household products to modify, the physical form, function, aesthetics and rheology properties of the formulations so that the product is delivered in a convenient form for application by the end user. Shampoos, for example, are theologically modified to allow a portion of the formulation to be readily poured from a container and yet be retained in the palm of the user""s hand without flowing further. But, their use may lead to or be impeded by formulation problems, such as unfavorable interactions with other ingredients of the formulations. Commercial hair care and personal care formulations, in particular, often contain cationic and amphoteric surfactants, as well as salts, other polymers, non-aqueous solvents, oils, colorants, peroxides, acids, and bases. Hair conditioning compositions, for example, frequently include cationic surfactants as conditioning agents for improving conditioning and detangling of the hair. See, for example, U.S. Pat. No. 5,100,657 which discloses quaternary ammonium-containing cationic surfactants, such as dialkyldimethylammonium chlorides and salts of fatty amines. The interaction of the thickening polymer with these formulation ingredients results in substantial viscosity reduction, formation of insoluble complexes or produce xe2x80x9cstringyxe2x80x9d or viscous rheology. The natural cellulosic gums, even if modified to make them cationic thickeners, still tend to be unacceptable in terms of their rheology, which will include stringy, and elastic rheologies, which are esthetically and functionally undesirable in a final formulation.
In addition, cations, from, e.g., cationic and amphoteric surfactants, are commonly employed in the formulations of cosmetic, personal care, household, textiles paper coating and printing, pharmaceutical and other products such as shampoos, conditioners, hair gels, mousses, hand cleaning soaps, oral delivery compositions such as syrups, as carriers for drugs in tablet form, in dental products, such as toothpaste and the like. A problem is that surfactants in a system may tend to disrupt the thickening mechanism, so that the thickeners tend to lose their viscosity in the presence of the surfactants typically used in cosmetic compositions. Anionic polymeric thickeners which are known to thicken and maintain the viscosity of cosmetic, and other formulations in an efficient and aesthetic manner, do not maintain their viscosity in the presence of cationic surfactants. Some nonionic thickeners can maintain the viscosity of cationic or amphoteric surfactant-containing formulations, however they have the problem that they produce elastic or xe2x80x9cstringyxe2x80x9d formulations which tend to flow as a single mass and are aesthetically unacceptable.
Hydrophilic polymers have been used for many years in bioadhesion systems in dentistry, orthopaedics, drug delivery, and surgical applications. The term xe2x80x9cbioadhesionxe2x80x9d has been used to describe phenomena related to the ability of some synthetic and biological macromolecules and hydrocolloids to adhere to biological tissues. For drug delivery, natural and synthetic bioadhesive polymers of different ionic charge (neutral, anionic, or cationic) are selected for their bioadhesive properties. The pH of the body varies throughout the digestive system. The stomach, for example, has a pH of around 1 to 2, whereas the intestinal tract has a pH in the range of 5 to 8. By selecting polymers with suitable ionic charge, the site of adsorption can be varied according to the pH. More recently, there has also been a significant interest in the use of hydrophilic polymers as bioadhesive materials in other areas, such as soft tissue-based artificial replacement and controlled release systems for local release of bioactive agents. Such applications include systems for release of drugs in the buccal or nasal cavities and for intestinal or rectal administration. For example, Blanco-Fuente et al. discloses the bioadhesive properties of natural cellulosic and crosslinked acrylic acid polymers. (Int. J. Pharm. 138, pp. 103-112 (1996)). The bioadhesive properties of poly N-vinylpyrrolidone (PNVP), and poly hydroxyethylmethacrylate (PHEMA) have been reported by Robert et al. (Acta Phar. Tehnol., 34 (2) pp. 95-98 (1988)). Natural cationic materials, such as chitosan have also been found to exhibit good bioadhesive properties. However, because such polymers are sometimes incompatible with certain active agents, such as medicines, which are to be delivered, there exists a need for polymers having bioadhesive properties which will provide that compatibility and perform at the desired pH levels.
In some cases, hydrophilic polymer systems have been used as therapeutic agents themselves. Burt et al. (J. Pharm. Sci. 76 (5), pp. 379-383 (1987)) discloses the use of an anion-exchange resin for binding phosphate in the blood. Phosphorus is present in the many sources of protein foods. In people with healthy kidneys, excess phosphorus is excreted in their urine. However, in patients with chronic renal failure, the kidneys are unable to maintain a delicate balance between phosphorus and calcium levels in the blood. Phosphorus is not excreted efficiently and thus builds up in the blood, a condition called hyperphosphatemia. Uncontrolled hyperphosphatemia causes a calcium-phosphate complex to precipitate in soft tissues, such as arteries, essentially turning them into bone. Hyperphosphatemia also causes increased secretion of the parathyroid hormone, which in turn causes bone degradation. Because a reduced dietary amount of phosphate is generally inadequate in reversing hyperphosphatemia, oral administration of certain phosphate binders has been suggested. Phosphate binders include calcium or aluminum salts which complex with phosphate to form insoluble calcium and aluminum salts. The long use of calcium and aluminum salts leads to hypercalcemia and aluminum toxicity.
Anion-exchange resins, some in the chloride form, have been recently suggested for use in binding phosphate and in the treatment of hyperphosphatemia. However, due their poor binding efficiency, high dosages are needed for a significant reduction in the absorbed phosphate. U.S. Pat. No. 5,667,775, for example, discloses using amine-containing crosslinked homopolymers for binding phosphate. Poly (allylamine) crosslinked with epichlorohydrin has shown some effectiveness as a phosphate binder. However, such compositions tend to be unsuited to oral administration. They are not readily absorbed into the bloodstream from the digestive system.
Another area of potential use of polymers is in absorption enhancers. For drugs that are administered orally, the drug must be transported from the digestive system into the blood stream. A membrane separates the intestinal tract from the blood stream. There are a number of ways in which materials, such as drugs pass through the membrane. In one transport system the material passes directly through the outer layer of cells, the epithelial layer. In a second system, receptors in the cells attract the material and push it through. In a third system, the material passes between cells. In this latter, xe2x80x9cparacellularxe2x80x9d transport mechanism, the normally tight junction between the cells is opened in order for the material to pass through. Some compounds are known to influence the absorption of drugs by assisting the opening of these junctions. Several different types of absorption enhancers, such as surfactants, fatty acids, chelating agents, and polymeric (anionic and cationic) materials have been tried with limited success. For example, Borchart et al. discloses the use of chitosan glutanate (a naturally occurring cationic polysaccharide) and crosslinked polyacrylic acids, such as Carbopol(copyright) 934, as absorption enhancers for insulin. (G. Borcard et al., J. Controlled Release 29, p. 39 (1996)).
The present invention provides for a new hydrophilic ampholylic polymer which overcomes the above-referenced problems, and others.
The present invention is a novel, hydrophilic ampholytic polymer or copolymer, having both cationic and anionic groups, formed by copolymerization of amino-functional and carboxy-functional ethylenically unsaturated monomers together with a hydrophilic, non-ionic monomer of high glass transition temperature (Tg) and, optionally, a cross linking monomer. The copolymer dissolves readily in water and builds up viscosity when added to water-based compositions. It is also useful as a bioadhesive and for other pharmaceutical applications.
In accordance with another aspect of the present invention, a method of preparing a hydrophilic ampholytic copolymer is provided by copolymerizing the requisite monomer components.
The new polymer is compatible with cationic materials, such as quaternized surfactants and is particularly suited to use in personal care compositions, such as shampoos, hair conditioners, hair gels, and various other cosmetic compositions where cationic surfactants are frequently used. It should be appreciated, however, that the material is also applicable to use in a wide range of water-based compositions for modifying the rheology of the composition or increasing viscosity, such as household products, cleaning compositions, toothpaste, pharmaceutical products, and the like. The material also finds application in drug delivery compositions and in the selective removal of ions, such as phosphates, from body fluids.
In accordance with other aspects of the present invention, the copolymer is compatible with acids and may be incorporated into acidic formulations, such as those containing organic and inorganic acids at low pH, shampoo and conditioning formulations, including those containing cationic surfactants, fabric softeners, personal care and household cleaning formulations, and pharmaceutical products.
One advantage of the present invention is the provision of a polymeric thickener which is compatible with high levels of cationic surfactants.
Another advantage of the present invention is that the polymer readily disperses in aqueous formulations and is capable of thickening aqueous formulations over a wide range of pH.
Yet another advantage of the present invention is that the polymer can be used in combination with anionic, cationic and non ionic systems.
A still further advantage of the present invention is that the polymer is amino functionalized and can deliver conditioning, anti-static, and improved adhesion to biosubstrates, such as hair, skin, and internal membranes of the gastrointestinal system, and as enzyme inhibitors.
The present invention is a hydrophilic ampholytic polymer or copolymer formed by copolymerization of:
a) 0.05 to 20 mole percent of at least one anionic monomer having at least one carboxy-functional group,
b) 10 to 45 mole percent of at least one cationic monomer having at least one amino-functional group,
c) a sufficient quantity (in an amount of about 35 to about 95 mole percent) of at least one non-ionic hydrophilic monomer to provide a glass transition temperature of above about 50xc2x0 C.,
d) 0 to 10 mole percent of a fourth hydrophobic monomer, and
e) 0 to 1.5 mole percent of a cross-linking monomer.
A variety of conventional polymerization techniques can be used to prepare the polymer, such as for example, solution, suspension, dispersion, or emulsion polymerization. A preferred method of preparation is by precipitation or inverse suspension polymerization of the polymer from a polymerization media in which the monomers are dispersed in a suitable solvent. When the copolymer has a Tg of greater than 50xc2x0 C., it can be precipitated from the polymerization media as a non-coalescing fine powder.
The monomers employed in preparing the copolymer are preferably water soluble and sufficiently soluble in the polymerization media to form a homogeneous solution. They readily undergo polymerization to form polymers which are water-dispersible or water-soluble.
Anionic monomers useful in forming the copolymer have at least one carboxy-functional group, such as an ethylenically unsaturated carboxylic acid having the structure which follows: 
where
R1=xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2CH3, and
R2=xe2x80x94(CH2xe2x80x94)n, where n=1 to 40, linear or branched alkyl, cycloalkyl, aryl, a polyethylene oxide chain having the formula xe2x80x94(CH2xe2x80x94CH2xe2x80x94Oxe2x80x94)p where p=1 to 50, or a polypropylene oxide chain having the formula xe2x80x94(CH2(CH3)xe2x80x94CH2xe2x80x94Oxe2x80x94)p where p=1 to 100.
Examples of ethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid, and sulfoalkyl esters of unsaturated carboxylic acids, such as 2-sulfoethyl methacrylate, alone or in combination. Particularly preferred anionic monomers are methacrylic acid and acrylic acid.
Cationic monomers useful in forming the copolymer include at least one amino-functional group. In the copolymer, the amino groups ionize in the presence of an acid and thicken. The cationic monomer can be one having the following structures: 
where
R1=xe2x80x94H, xe2x80x94CH3, or xe2x80x94CH2CH3,
R2=xe2x80x94[CH2xe2x80x94]n, where n=1 to 40, linear or branched alkyl, cycloalkyl, aryl, a polyethylene oxide chain having the formula xe2x80x94(CH2xe2x80x94CH2xe2x80x94Oxe2x80x94)p where p=1 to 50, or a polypropylene oxide chain having the formula xe2x80x94(CH2(CH3)xe2x80x94CH2xe2x80x94Oxe2x80x94)p where p=1 to 50, R3, R4, Y1, Y2, and Y3 may be xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH3, branched or linear alkyl, aryl, cycloalkyl, or combinations thereof.
Examples of cationic monomers include the following:
1) acrylamides, methacrylamides, vinyl amines, diallyl amines, vinyl heterocyclic amides, and combinations thereof, including N-(dimethylaminobutyl)acrylamide, N-(dimethylaminobutyl) methacrylamide, N-(dimethyl aminopropyl)acrylamide, N-(dimethylaminopropyl) methacrylamide, N-(dimethylaminoethyl)methacrylamide, N-(dimethylaminoethyl) acrylamide; N-(dimethylaminomethyl)acrylamide, N-(dimethylaminomethyl)methacrylamide, N-(diethylaminopropyl)acrylamide, N-(diethylaminopropyl) methacrylamide, N-(dimethylaminoethyl) methacrylamide, N-(diethylaminoethyl)acrylamide, with N-(dimethylaminopropyl) methacrylamide being preferred.
2) acrylates and methacrylates selected such as N-(dimethylaminomethyl) acrylate, N-(dimethylaminomethyl) methacrylate, N-(dimethylaminopropyl) acrylate, N-(dimethylaminopropyl) methacrylate, N-(dimethylaminomethyl) acrylate, N-(dimethylaminoethyl) methacrylate, N-(dimethylaminoethyl)acrylate, N-(diethylaminoethyl) acrylate, N-(diethylaminoethyl) methacrylate, N-(2-methacryloyloxyethyl) ethylene urea, N-(diethylaminoethyl) methacrylate, N-(dimethylaminopropyl) methacrylate, and their chloride, sulfate, and sulfonate salts, as well as vinyl amines, such as vinyl pyridine and vinyl morpholine, diallyl amines, and their sulfate, sulfonate and chloride salts, dimethylaminoethyl methacrylate and their chloride and sulfonate salts being preferred;
3) chloride, sulfate, and sulfonate salts of N-(dimethylaminopropyl) acrylate, N-(dimethylaminobutyl) methacrylate, N-(dimethylaminobutyl) acrylate, N-(dimethylaminopropyl) methacrylate, N-(dimethylaminoethyl) methacrylate, N-(dimethylaminoethyl) acrylate, N-(diethylaminoethyl) methacrylate, N-(dimethylaminopropyl) methacrylamide;
4) aromatic and aliphatic vinyl or allyl amines selected from the group consisting of vinyl amine, vinyl piridine, vinyl morpholine, vinyl imidazole, dimethyl aminomethyl styrene, dimethyl aminoethyl styrene and their chloride, bromide, sulfate, sulfonate, phosphate, methyl and ethyl sulfonate salts;
5) diallyl amines having the following structure: 
xe2x80x83where R1 may be: xe2x80x94H, xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH3, branched or linear alkyl, aryl, cycloalkyl, or combinations thereof.
R2 is an acid radical such as chloride, bromide, sulfate, sulfonate, phosphate, methyl or ethyl sulfonate; and
6) combinations thereof.
While the cationic and anionic monomers have been described as separate monomers, it should be understood that a single monomer, having both an amino-functional and a carboxy-functional group could be substituted for the two types of monomers.
For ease of separation from a solvent media, the monomers are selected such that the resultant copolymer has a Tg of greater than about 50xc2x0 C. This allows the copolymer to be isolated in the form of a powder by precipitation from the reaction mixture. However, a number of low Tg monomers can also be used in relatively small quantities without compromising the formation of the copolymers.
The non-ionic hydrophilic monomers are selected to impart water solubility to the resultant polymer and preferably are those that usually will enable achieving a high Tg in the resultant copolymer Exemplary non-ionic monomers include ethylenically unsaturated amides having the following structure: 
where R1 is xe2x80x94H, xe2x80x94CH3 or xe2x80x94CH2CH3, and
where R3 and R2 are selected from the group consisting of H, OH, methyl, ethyl, lauryl, stearyl, carboxy, and amino groups, and combinations thereof. In particular, the monomers consisting of acrylamide, methacrylamide, methyl acrylamide, dimethyl acrylamide, fumaramide, diacetone acrylamide, and dimethyl methacrylamide are preferred.
Other examples include fumaramide; N-vinyl pyrrolidone; hydroxyethyl methacrylate (HEMA); hydroxyethyl acrylate (HEA); hydroxypropyl acrylate; methylol acrylamide; hydroxypropyl methacrylate. Other suitable non-ionic hydrophilic monomers belong to the family of methoxy-polyethylene-oxide, acrylates, methacrylates and can be represented by the following structure: 
where R1 is xe2x80x94H, xe2x80x94CH3, or xe2x80x94CH2CH3, and
where R2 is H, OH, methyl, ethyl, lauryl, stearyl, carboxy or an amino group, alone or combinations thereof and n=1 to 100. Monomers of the type represented in the structure tend to lower the Tg of the copolymer. Consequently, they are preferably added in relatively small amounts.
Other non-ionic hydrophilic monomers can be cyclic amides having the following structure: 
where R is an alkylene group such as xe2x80x94[CH2xe2x80x94]n, n=1 to 4, such as vinyl pyrrolidone (n=1), vinyl caproclactam (n=2), or any combination of non-ionic monomer can be used.
Particularly preferred hydrophilic monomers are hydroxyethyl methacrylate, hydroxyethyl acrylate, methacrylamide, vinyl pyrrolidone, and hydroxypropyl methacrylate.
Table 1 lists the glass transition temperatures Tg of homopolymers formed from selected monomers suitable for incorporation in the copolymer of the present invention.
Optionally, a hydrophobic monomer is employed to modify the properties of the resulting copolymer. Suitable hydrophobic monomers include those which are (1) water-insoluble, (i.e., less than 0.2 weight part of the hydrophobic monomer will dissolve in 100 weight parts of water) and (2) ethylenically unsaturated compounds having hydrophobic associative groups, herein referred to as hydrophobic moieties usually added at less than 2% mol of the total copolymer composition. The hydrophobic monomer increases the thickening efficiency of the copolymer through inter molecular, non-polar association.
The hydrophobic moieties preferably have at least 4 carbon atoms and are most preferably pendant organic groups having hydrophobic character comparable to one of the following: aliphatic hydrocarbon groups having at least four carbons such as C4 to C20 alkyls and cycloalkyls; polynuclear aromatic hydrocarbon groups such as napthyls; alkylaryls, wherein the alkyl has one or more carbons, preferably 4 to 8 carbons; haloalkyls of 4 or more carbons, preferably perfluoroalkyls; polyalkyleneoxy groups wherein the alkylene is ethylene, propylene or a higher alkylene and there is at least 1 alkyleneoxy unit per hydrophobic moiety. The hydrophobic monomers are represented by the following formulas: 
where
R1 is selected from hydrogen, methyl and ethyl groups,
R2 and R3 is selected from alkyl groups having from 1 to 30 carbon atoms. They can be linear or branched,
R2 and R3 can also be selected from hydrogen or methoxy terminated oxyethylene and oxypropylene groups with structure:
xe2x80x94[CH2xe2x80x94CH2xe2x80x94Oxe2x80x94]n xe2x80x94[CH2(CH3)xe2x80x94CH2xe2x80x94Oxe2x80x94]n
where n is an integer from 1 to 100.
Exemplary hydrophobic monomers include the higher alkyl esters of xcex1, xcex2-ethylenically unsaturated carboxylic acids, such as dodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecyl methacrylate, tetradecyl acrylate, tetradecyl methacrylate, octadecyl acrylate, octadecyl methacrylate; ethyl half esters of maleic anhydride, diethyl maleate; and other alkyl esters derived from the reactions of alkanols having from 4 to 20, preferably from 8 to 20, carbon atoms with ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, itaconic acid and aconitic acid; alkylaryl esters of ethylenically unsaturated carboxylic acids such as nonyl-∀-phenyl acrylate, nonyl-∀-phenyl methacrylate, dodecyl-∀-phenyl acrylate and dodecyl-∀-phenyl methacrylate; N-alkyl, ethylenically unsaturated amides such as N-octadecyl acrylamide; N-octadecyl methacrylamide, N,N-dioctyl acrylamide and similar derivatives thereof; ∀-olefins, such as octene-1, decene-1, dodecene-1, and hexadecene-1; vinyl alkylates wherein the alkyl has at least 8 carbons, such as vinyl laurate and vinyl stearate; vinyl alkyl ethers, such as dodecyl vinyl ether and hexadecyl vinyl ether; N-vinyl amides such as N-vinyl lauramide and N-vinyl stearamide; and ar-alkylstyrenes such as t-butyl styrene.
Of the foregoing, the preferred hydrophobic monomers are the alkyl esters of acrylic acid, methacrylic acid, N-alkyl acrylamides and N-alkyl methacrylamides, wherein the alkyl has from 8 to 20 carbon atoms, and the alkyl styrenes, wherein the alkyl has from 4 to 8 carbons. The alkyl methacrylates, wherein the alkyl has from 10 to 20 carbon atoms. Dodecyl methacrylate and N-dodecyl methacrylamide are the most preferred hydrophobic monomers. One or more hydrophobic monomers may be used, depending on the desired properties of the copolymer.
With regard to the polymerization solvent of choice for use in the polymerization process, the solubility parameter of the solvent is preferably close to that of the selected monomers. The solubility parameter has been defined as the square root of the cohesive energy density which represents the concentration of forces which cause molecules to cohere. If the solubility parameter of the solvent is much higher than that of one of the monomers, either the monomer does not dissolve readily in the solvent, or the resulting copolymer has a tendency to precipitate too quickly, and its effectiveness as a thickener is reduced. If the solubility parameter of one of the monomers is substantially higher than that of the solvent, the resulting copolymer has a tendency to swell. As a result, mixing of the polymerization media becomes difficult. Preferably, the solubility parameters of the monomers are no more than 2 (MPa)xc2xd below that of the solvent. Table 2 lists a number of monomers and solvents and their corresponding solubility parameters.
As can be seen from Table 2, the preferred solvent varies with the choice of monomers. For example, monomers such as n-vinyl pyrrolidone (NVP), hydroxyethyl methacrylate (HEMA), dimethyl aminopropyl methacrylamide (DMAPMA), Methyl Methacrylate (MAA), and Acrylic Acid (AA) are compatible with cyclohexane, ethyl acetate, and butyl acetate solvents. HEA, CD 550, and CD 552 polymerize well in ethyl acetate.
The selected solvent may be a blend of two or more solvents. This allows the solubility parameter range to be adjusted so that the solvent is compatible with the chosen monomers. One preferred blend of solvents is a blend of a hydrocarbon, such as cyclohexane, with an alkyl acetate ester, such as ethyl acetate. Particularly preferred solvents have a boiling point of below 100xc2x0 C. so that they can be removed from the copolymer by evaporation under moderate temperature and pressure conditions.
Examples of suitable polymerization solvents are aliphatic hydrocarbons, such as pentane, hexane, heptane, cyclohexane; mineral spirits; mineral oils; branched hydrocarbons, such as those distributed by Presperse, Piscataway, N.J., under the trade name of Permethyl 97A to 106A; ethers, such as dimethyl ether and diethyl ether, esters, such as n-butyl acetate, t-butyl acetate, propyl acetate, ethyl acetate, and methyl acetate; aromatic hydrocarbons such as benzene, toluene, and xylene; perfluorinated fluids, such as perfluorohexane, perfluorooctane, perfluoroalkyl ether, perfluoroalkyl amines, and trifluoro ethanol; alcohols, such as t-butyl alcohol, isopropyl alcohol, and methanol; and halogenated solvents such as methylene chloride. The solvents may be used alone or in combination.
A cross-linking monomer, or crosslinker is added to the polymerization media to modify and control the properties achieved by the resulting copolymer. This would give a formulation, thickened with the polymer of the present invention, an aesthetically desirable appearance and rheology and allow portions of the product to be dispensed as required. For example, a hair gel or toothpaste will flow out of a squeezable tube for application, while the remaining product pulls back to remain with the package after release of the pressure.
The cross-linking monomer employed is represented by the formula: 
n, m=1 to 4, n+mxe2x89xa72
R1, R3=H, alkyl
R2=alkyl, cycloalkyl, aryl,
=xe2x80x94(CH2xe2x80x94CH2xe2x80x94O)pxe2x80x94 where p=1 to 50,
=xe2x80x94(CH2(CH3)xe2x80x94CH2xe2x80x94O)pxe2x80x94 where p=1 to 50,
=amido, ester, polyamido, polyester
Suitable cross-linking monomers include di-, tri- or poly-functional monomers of vinyl, allyl, acrylic or methacrylic, acrylamido or methacrylamido.
Examples include triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, ethylene glycol diacrylate, triacrylate, trimethylol propane trimethacrylate, allyl methacrylate, allyl citrate, di- and tri-allyl amine, polyethylene glycol di- and tri-acrylates, allyl pentaerythritol, allyl sucrose, and methylenebisacrylamide. Particularly preferred cross-linking monomers are ethylene glycol dimethacrylate, trimethylol propane trimethacrylate, allyl pentaerythritol, and triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.
Optionally, the hydrophilic ampholytic polymer of the present invention can be a linear un-cross-like linked polymer. Such polymers would be useful for scale inhibition, dispersant applications, and general purpose viscosity modification, especially in the presence of cationic materials.
An initiator is used to catalyze the polymerization reaction. Any conventional free radical initiator can be used, including azo- and peroxo-type initiators. Examples of suitable azo-type initiators are azobis-dimethylvaleronitrile, azobis-isobutyronitrile, azobis-methylbutyronitrile and other azo-initiators sold by DuPont, under the trade name VAZO(copyright), and by WAKO Pure Chemical Industries, under the trade names of V-40 to V501.
Examples of suitable peroxo-type initiators include lauryl peroxide, cumene hydroperoxide, ethyl hexyl peroxodicarbonate, diisopropyl peroxydicarbonate, 4-(t-butylperoxylperoxycarbonyl)-3 -hexyl-6-7-(t-butyl-peroxycarbonyl)heptyl cyclohexene (4-TBPCH), cumene hydroperoxide and t-butyl peroxyneodecanoate, t-butyl hydroperoxide, benzoyl peroxide, and other organic peroxides sold by Elf Atochem North America, Inc., under the trade names of Lupersol(copyright), Luperco(copyright), Lucidol(copyright), and Luperox(copyright).
In particular, a preferred initiator is 2,2xe2x80x2-azobis(2-methylbutyronitrile), sold by DuPont under the trade name VAZO(copyright) 52. Other methods suitable for the polymerization of ethylenically unsaturated monomers such as cationic, anionic or redox-pair initiators can also be used to prepare the ampholytic polymers of this invention.
The monomers, cross-linking monomer, and initiator are preferably combined in the polymerization media in the following proportions:
Particularly preferred ranges of monomers are:
The preferred ratio of monomer is determined by the percent mole ratio of cationic to anionic monomer as follows:
Ratio (R)=Cationic Monomer÷Anionic Monomer
A preferred ratio of cationic monomers to anionic monomers is from about 2 to about 16, with the ratio of about 3 to 16 being further preferred. Selecting a ratio within this range has two advantages. First, it facilitates polymerization. The cationic and anionic monomers form inter and intra salt units which cause the copolymer to precipitate from the solvent in the form of a fine powder. This facilitates formation of the copolymer by precipitation polymerization. Second, the presence of anionic and cationic groups in the same polymeric molecule renders the copolymer compatible with cationic, anionic, and amphoteric surfactants typically used in cosmetic, household, cleaning, pharmaceutical, and other formulations.
The preferred ratio of monomers to solvent, i.e., the total solids, is from about 10 to about 30% by weight of the contents of the reactor. At about 30% by weight, or above, the reaction is difficult because reactants tend to form gels or solidify as a compacted mass inside the reactor, making processing of the copolymer difficult, unless some means for reducing the viscosity or facilitating the reaction is employed.
Other polymerization additives, such as non-ionic surfactants, polymeric stabilizers, dispersing agents, acids, bases, and salts, can be used, either during or post polymerization. Such polymerization additives are used to facilitate polymerization by preventing agglomeration of the polymer particles as they are formed in the reactor.
Suitable nonionic surfactants for this purpose are added at from about 0.01% wt to 4% wt of the total mass in the reactor and include those with a hydrophobic/hydrophilic balance (HLB) of from about 2 to 16. Most preferred are those with an HLB of 2 to 8. Exemplary surfactants include alkyl polyethyleneoxy compounds represented by the formula:
RO(EO)nxe2x80x94H,
wherein R is a C8 to C18 alkyl, EO is ethyleneoxy and n is an integer from 1 to 10. Of the foregoing surfactants, the ethoxylated alkyl phenol and ethoxylated fatty alcohols are more preferred. Other suitable nonionic surfactants include those described in McCutcheon""s, Detergents and Emulsifiers, North American Edition, 1980 Annual, ones sold by ICI Co. under the trade name, Hypermer polymeric surfactants or dispersants, and glycols and dimethicone copolyols, most broadly known as polysiloxane polyether copolymers, represented by the formula: 
where
x=2-200;
y=2-100;
PE=(CH2)pO(EO)m(PO)nZ, alkyl radical, (Me2SiO)pZ
xe2x80x83where EO=xe2x80x94CH2CH2Oxe2x80x94, ethyleneoxy;
PO=xe2x80x94CH2CH(CH3)O, 1,2-propyleneoxy;
p=2-30;
m=0-100;
n=0-100; and
Z=alkyl radical.
A number of polymers of this type are available from Witco Co. under the trade name of Silwet, from Dow Corning under the trade names, DC or DC Surfactant, and from Goldshmidt Co. under the trade name, Abil surfactants.
To prepare the copolymers of the present invention, the selected monomers, crosslinker, solvent, and surfactant are mixed to form a homogenized solution. The mixture is blanketed with an inert gas, such as nitrogen, and heated to about 30-90xc2x0 C., more preferably, about 40-60xc2x0 C. A first portion of initiator, or batch initiator, is added and the reactants stirred for a period sufficient for polymerization, typically about 5 hours. A second portion of initiator, or xe2x80x9ckickxe2x80x9d initiator, is added when polymerization is essentially complete. This reduces the concentration of any residual monomers by copolymerizing them. The xe2x80x9ckickxe2x80x9d initiator may be the same as the batch initiator, or a different initiator.
Alternatively, one or more of the monomers is added incrementally, with a portion of the monomer being added following the addition of the initiator.
During the reaction, the copolymer precipitates from the solvent as a fine powder. This forms a slurry with the solvent. The solvent is removed, for example by rotary evaporation. The copolymer product may be further dried to complete solvent removal. The copolymer remains as a powder or friable solid.
The copolymers formed are effective rheology modifiers and thickeners for a wide variety aqueous formulations, including organic acid formulations, inorganic acid formulations, hair conditioners, shampoos, fabric softeners, and the like, pharmaceutical, personal care and household formulations. The formulations show good retention of viscosity over a wide range of pH and in the presence of cationic surfactants.
The copolymer is compatible with a variety of hair conditioning agents, including silicone conditioning agents, cationic surfactant conditioning agents, amphoteric surfactants, and other conditioning agents found in hair care compositions and personal care products.
Examples of compatible silicone conditioning agents include volatile silicones, such as cyclic or linear polydimethyl siloxanes of the general formula:
(CH3)3Sixe2x80x94Oxe2x80x94[xe2x80x94Si(CH3)2xe2x80x94Oxe2x80x94]nxe2x80x94Si(CH3)3
where n is an integer from 1-7.
The copolymer is also compatible with non-volatile silicone conditioning agents, such as polydimethylsiloxane gums, aminosilicones and phenyl silicones, such as polyalkyl or polyaryl siloxanes. Particularly preferred silicones of this type are polydimethyl siloxane, polydiethyl siloxane, and polymethylphenylsiloxane.
Other silicone cationic polymers which are compatible with the copolymer correspond to the formula:
(R1)aG3axe2x80x94Sixe2x80x94(xe2x80x94OSiG2)nxe2x80x94(xe2x80x94OSiGb(R1)2b)mxe2x80x94Oxe2x80x94SiG3a(R1),
where G is selected from the group consisting of hydrogen, phenyl, OH, C1-C8 alkyl groups, preferably methyl, and where a denotes 0 or an integer from 1 to 3, and preferably equals 0; b denotes 0 or 1, and preferably equals 1; the sum n+m is a number from 1 to 2,000, and preferably from 50-150, n denoting an integer from 0 to 1,999, and preferably from 49-149, and m denoting an integer from 1 to 2000, and preferably from 1 to 10; R1 is a monovalent radical of the general formula CqH2qL, where q is an integer from 2 to 8 and L is selected from the groups xe2x80x94N(R2)CH2xe2x80x94CH2xe2x80x94N(R2)2 and xe2x80x94N(R2)2, where R2 is selected from the group consisting of hydrogen, phenyl, benzyl, and saturated hydrocarbon radicals, preferably alkyl radicals containing from 1 to 20 carbon atoms.
Rigid silicone polymers are also compatible with the present copolymer. These include polydimethyl siloxane gums and polyphenyl methyl siloxane gums, commonly known as dimethicone, amodimethicone, phenylmethicone. Examples include filler reinforced polydimethyl siloxane gums, such as those having end groups such as hydroxyl; cross-linked siloxanes, such as organic substituted silicone elastomers; organic substituted siloxane gums, including those having end groups such as hydroxyl; resin reinforced siloxanes; and cross-linked siloxane polymers. One such siloxane gum is a diphenyl-dimethyl polysiloxane gum having a molecular weight of at least about 500,000 and which is diphenyl-substituted.
Silicone resins compatible with the copolymer are silicone polymers with a high degree of cross linking introduced through the use of trifunctional and tetrafunctional silanes. Typical silanes used in the manufacture of such resins include monomethyl, dimethyl, monophenyl, diphenyl, methylphenyl, monovinyl, and methylvinyl chlorosilanes, and tetrachlorosilane. Other functional silicone materials include silicone glycol copolymers, such as those sold by Dow Corning Corp., Midland, Mich., under the trade names DC 190 and DC 193.
Cationic surfactant conditioning agents compatible with the copolymer include quaternary ammonium salts, such as dialkyldimethylammonium chlorides, wherein the alkyl groups have from about 12 to about 22 carbon atoms and are derived from long-chain fatty acids, such as hydrogenated tallow fatty acid (tallow fatty acids yield quaternary compounds wherein R1 and R2 have predominantly from 16 to 18 carbon atoms). Examples of such quaternary ammonium salts include ditallowdimethyl ammonium chloride, ditallowdimethyl ammonium methyl sulfate, dihexadecyl dimethyl ammonium chloride, di(hydrogenated tallow) dimethyl ammonium chloride, dioctadecyl dimethyl ammonium chloride, dieicosyl dimethyl ammonium chloride, didocosyl dimethyl ammonium chloride, di(hydrogenated tallow) dimethyl ammonium acetate, dihexadecyl dimethyl ammonium chloride, dihexadecyl dimethyl ammonium acetate, ditallow dipropyl ammonium phosphate, ditallow dimethyl ammonium nitrate, di(coconutalkyl) dimethyl ammonium chloride, and stearyl dimethyl benzyl ammonium chloride. Ditallow dimethyl ammonium chloride, dicetyl dimethyl ammonium chloride, stearyl dimethyl benzyl ammonium chloride, cetyl trimethyl ammonium chloride, and behenyl trimethyl ammonium chloride are preferred quaternary ammonium salts useful herein. Di-(hydrogenated tallow) dimethyl ammonium chloride is a particularly preferred water-insoluble quaternary ammonium salt for use as a conditioning agent in hair care compositions which is also compatible with the present copolymer.
Salts of primary, secondary, and tertiary fatty amines are also preferred water-insoluble cationic surfactant materials for use as hair conditioning agents which are compatible with the present copolymer. The alkyl groups of such amines preferably have from about 12 to about 22 carbon atoms, and may be substituted or unsubstituted. Secondary and tertiary amines are preferred, tertiary amines are particularly preferred. Such amines, useful herein, include stearamido propyl dimethyl amine, diethyl amino ethyl stearamide, dimethyl stearamine, dimethyl soyamine, soyamine, tridecyl amine, ethyl stearylamine, ethoxylated (2 moles ethylene oxide) stearylamine, dihydroxyethyl stearylamine, and arachidylbehenylamine. Suitable amine salts include the halogen, acetate, phosphate, nitrate, citrate, lactate, and alkyl sulfate salts. Such salts include stearylamine hydrochloride, soyamine chloride, stearylamine forrnate, N-tallowpropane diamine dichloride, stearamidopropyl dimethylamine citrate, stearamido propyldimethyl amine, and guar hydroxypropyl triammonium chloride.
Amphoteric surfactants compatible with the present copolymer include high alkyl betaines, sulfo betaines, amido betaines, and amidosulfobetaines, such as cetyl betaine, and derivatives of aliphatic secondary and tertiary amines in which the aliphatic radical can be straight chain or branched and wherein one of the aliphatic substituents contains from about 8 to about 18 carbon atoms and one contains an anionic water solubilizing group, such as carboxy, sulfonate, sulfate, phosphate, or phosphonate. Examples of compounds falling within this definition are sodium 3-dodecylaminopropionate, N-alkyltaurines such as the one prepared by reacting dodecylamine with sodium isethionate, and N-higher alkyl aspartic acids. Others include alkyl, preferably C6-C22 and most preferably C8-C12, amphoglycinates; alkyl, preferably C6-C22 and most preferably C8-C12, amphopropionates; and mixtures thereof.
Suitable zwitterionic surfactants for use in hair care compositions and which are compatible with the present copolymer are exemplified by those which can be broadly described as derivatives of aliphatic quaternary ammonium, phosphonium, and sulfonium compounds, in which the aliphatic radicals can be straight chain or branched, and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water-solubilizing group, such as a carboxy, sulfonate, sulfate, phosphate, or phosphonate group. Examples include alkyl amino sulfonates, alkyl betaines, and alkyl amido betaines.
Additional hair conditioning agents are used in hair care compositions to provide enhanced conditioning benefits, and which are also compatible with the present copolymer, are hydrolyzed animal and vegetable protein conditioning agents.
A common component in the preparations of cleaning compositions such as shampoo, hair conditioning, industrial and household cleaners, and detergent compositions is a synthetic anionic surfactant. The surfactants are present at a level of from about 5% to about 25%, preferably from about 15% to about 20% and are compatible with the polymers of the present invention. These synthetic anionic surfactants include alkyl and alkyl ether sulfates, represented by the formulae ROSO3 M and RO(C2 H4O)xSO3 M wherein R is alkyl or alkenyl of about 10 to about 20 carbon atoms, x is 1 to 10, and M is a water-soluble cation such as ammonium, sodium, potassium and triethanolamine. The alkyl ether sulfates useful in the present invention are condensation products of ethylene oxide and monohydric alcohols having about 10 to about 20 carbon atoms. Preferably, R has 14 to 18 carbon atoms in both the alkyl and alkyl ether sulfates. The alcohols can be derived from fats, e.g., coconut oil or tallow, or can be synthetic. Lauryl alcohol and straight chain alcohols are those derived from coconut oil. Such alcohols are reacted with 1 to 10, and especially 3, molar proportions of ethylene oxide and the resulting mixture of molecular species, having, for example, an average of 3 moles of ethylene oxide per mole of alcohol, is sulfated and neutralized.
Specific examples of alkyl ether sulfates for use with the present invention are sodium coconut alkyl trioxyethylene sulfate; lithium tallow alkyl trioxyethylene sulfate; and sodium tallow alkyl hexaoxyethylene sultate. Highly preferred alkyl ether sulphates are those comprising a mixture of individual compounds, said mixture having an average alkyl chain length of from about 12 to 16 carbon atoms and an average degree of ethoxylation of from about 1 to 4 moles of ethylene oxide. Such a mixture also comprises from about 0 to 20% by weight C12-13 compounds; from 60 to 100% by weight of C14-15-16 compounds, from about 0 to 20% by weight of C17-18-19 compounds; from about 3 to 30% by weight of compounds having a degree of ethoxylation of 0; from about 45 to 90% by weight of compounds having a degree of ethoxylation of from 1 to 4; from about 10 to 25% by weight of compounds having a degree of ethoxylation of from 4 to 8; and from about 0.1 to 15% by weight of compounds having a degree of ethoxylation greater than 8.
Another class of anionic surfactants, which are compatible with the polymers of the present invention, are the water-soluble salts of the organic, sulfonic acid reaction products of the general formula:
RSO3 M
wherein R is chosen from the group consisting of a straight or branched chain, saturated aliphatic hydrocarbon radical having from 8 to 24, preferably 12 to 18, carbon atoms; and M is a cation. Examples are the salts of an organic sulfuric acid reaction product of a hydrocarbon of the methane series, including iso-, neo-, ineso-, and n-paraffins, having 8 to 24 carbon atoms, preferably 12 to 18 carbon atoms and a sulfonating agent e.g., SO3, H2SO4, oleum, obtained according to known sulfonation methods, including bleaching and hydrolysis, such as alkali metal and ammonium sulfonated C12-18 n-paraffins.
Additional examples of anionic synthetic detergents which are compatible with the polymers of the present invention are the following:
a) the reaction product of fatty acids esterified with isethionic acid and neutralized with sodium hydroxide where, for example, the fatty acids are derived from coconut oil; sodium or potassium salts of fatty acid amides of methyl tauride in which the fatty acids, for example, are derived from coconut oil,
b) succinamates, which includes such surface active agents as disodium N-octadecylsulfosuccinamate; tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfo-succinamate; diamyl ester of sodium sulfosuccinic acid; dihexyl ester of sodium sulfosuccinic acid; dioctyl esters of sodium sulfosuccinic acid,
c) olefin sulfonates having about 12 to about 24 carbon atoms, which includes compounds which can be produced by the sulfonation of alpha-olefins by means of uncomplexed sulfur trioxide, followed by neutralization of the acid reaction mixture in conditions such that any sultones which have been formed in the reaction are hydrolyzed to give the corresponding hydroxy-alkanesulfonates. The sulfur trioxide can be liquid or gaseous, and is usually, but not necessarily, diluted by inert diluents, for example by liquid SO2, chlorinated hydro-carbons, etc., when used in the liquid form, or by air, nitrogen, gaseous SO2, etc., when used in the gaseous form. The alpha-olefins from which the olefin sulfonates are derived are mono-olefins having 12 to 24 carbon atoms, preferably 14 to 16 carbon atoms. Preferably, they are straight chain olefins. Examples of suitable 1-olefins include 1-dodecene; 1-tetradecene; 1-hexadecene; 1-octadecene; 1-eicosene and 1-tetracosene,
d) betaalkyloxy alkane sulfonates, such as beta-alkyloxy-alkane-1-sulfonates, or alternatively 2-alkyloxy-alkane-1-sulfonates, having low hardness (calcium ion) sensitivity useful herein to provide superior cleaning levels under household washing conditions include: potassium beta-methoxydecanesulfonate, sodium 2-methoxytridecanesulfonate, potassium 2-ethoxytetradecylsulfonate, sodium 2-isopropoxyhexadecylsulfonate, lithium 2-t-butoxytetradecylsulfonate, sodium beta-methoxyoctadecylsulfonate, and ammonium-n-propoxydodecylsulfonate, and
e) other synthetic anionic surfactants such as those that are described in McCutcheon""s, Detergents and Emulsifiers, 1994, published by M.C. Publishing Corporation, which is incorporated herein by reference and in U.S. Pat. No. 3,929,678, Dec. 30, 1975 to Laughlin et al. The above-mentioned surfactants can be used alone or in combination in the shampoo compositions of the present invention. Mixtures of alkyl sulfates and ethoxylated alkyl sulfates are preferred for use herein.
Additionally, in many types of formulation compositions, the detergent system can be prepared by using non-ionic surfactants blends. The surfactant is present at a level of from about 5% to about 25%, preferably from about 15% to about 20%. Suitable detergent systems are composed of nonionic surfactants with hydrophobic/hydrophilic balance, HLB, from about 2 to 16. Most preferred are those with HLB=8-18. Examples of these surfactant include alkyl polyethyleneoxy compounds represented by the formula,
RO(EO)nxe2x80x94H,
wherein R is C8-C18 alkyl, or phenyl. EO is ethyleneoxy and n is a number from 1 to 100. Other suitable nonionic surfactants are described in McCutcheon""s, Detergents and Emulsifiers, 1994, M.C. Publishing Corporation. Of the foregoing surfactants, the ethoxylated alkyl phenol and ethoxylated fatty alcohols are more preferred. Alkanolamides such as Cocamide MEA, Cocamide DEA, and Lauramide DEA are just a few examples of the alkanolamides that may be used. Amine oxides such as cocamidopropylamine oxide stearamine oxide, lauramine oxide, and behenamine oxide.
To modify rheology and/or thicken a selected composition, the copolymer is added to the composition as a fine powder at a concentration of from about 0.01% wt. to 20% wt. and the mixture stirred. Heat may be applied to aid dispersability or dissolution of the copolymer. The copolymer is neutralized with an inorganic, organic, or amino acid to bring about the thickening process. The amount of acid required depends on the viscosity and pH of the desired formulation. Suitable acids for neutralization include, but not limited to, acetic, hydrochloric, hydrofluoric, hydroiodic, hydrobromic, nitric, phosphoric, sulfuric, polyacrylic, formic, glycolic, lactic, malic, citric, mandelic, and tartaric acids, carboxylic acids of the general formula RnCOOH, where n is an integer from 1 to 18, and amino acids in general.
The ampholytic copolymer is also suitable for the preparation of shampoos, conditioners, rinses, liquid soap, soap bars, detergents, cleaners, room deodorizers, and the like.
In general, the polymers of this invention can be used in a host of applications where the presence of acidic and basic groups in the same molecule is a useful property. They can be used as additives in cosmetic applications, body implants, coatings for catheters, cannulae, antiperspirant and deodorant formulations, coating for medical devices, gloves, removable protective coatings, wound dressings, etc. They can be used in the formulation of inks, protective washable coatings for textiles, etc. They can be used to thicken organic or inorganic acid systems.
The copolymer is suitable for use as thickening and/or conditioning additive in the formulation of hair creams, skin creams, lotions, pomades, and ointments, topical medicated creams, skin protective films, hair depilatories, hair shaving creams, hand and body lotions, mascaras, sunscreens, and the like.
The copolymer also finds application as an additive in nail care formulations, such as water-based nail polish, nail repair, nail protection, and the like.
In cosmetic applications, the copolymer can be used as a wet and dry conditioner, rinse out conditioner, in conditioning shampoo, conditioning styling gel, 2 in 1 conditioning body wash, conditioning/post treatment (color enhancing resins) of hair color, moisturizing body wash, skin moisturizer, protective cream, antiperspirants, alpha hydroxy acid (AHA) containing formulations, self tanning applications with dihydroxyacetone (DHA), skin whitening formulations containing kojic acid, natural extracts and hydroquinone.
The resultant copolymers can be used in home care or in fabric softener, disinfectant cleaner, bath room cleaners, toilet bowls, hand soaps, disinfectant, and alkali strippable vinyl floor polish formulations.
Another use is in formulating for medical applications as hand creams, antiviral (anionic viruses), antibiotic, gastric bio-adhesive, super-absorber in diaper applications, ion exchange, non drip sprayable disinfectant in hospitals, hard surface antimicrobial finish applied during routine maintenance, control release of drugs in stomach (low pH from tablets).
A further use is textile, inks and paper applications as flocculent for phenolics (paper mill effluent), paper coatings, antiwicking for ink jet inks, thickener for ink formulations such as cationic dyes for use in printing acrylic fabrics, binder for paper (anionic pulp), saturating non woven fabrics to obtain synthetic leathers, and protective washable coatings for textiles.
The polymer also finds utility in general industrial applications such as deck and fence wash, anti-freeze, shear thinning deicers, pickup acid and alkali spills, in water treatment, as crosslinkers for epoxy""s, as cement plasticizer, to stabilize asphalt emulsions at low pH, to make clear adhesives, as dispersion stabilizer of clay, titanium dioxide, calcium carbonate and other minerals, pickling agents in cold rolled steel process, industrial metal coatings at low pH, extracting microbes from aqueous systems, leather processing aid (bonds with the carboxylated proteins).
The copolymer can also be used in the formulation of pharmaceutical formulations, such as creams, pomades, gels, tooth paste, tablets, gel capsules, enema fluids, vomitives, suppositories, foamed anti-fungal preparations. The copolymer can be used as a vehicle in topical and systemic drug delivery compositions, compositions to deliver transdermally active ingredients to or through the skin, ocular fluids, anti-acne formulations, topical analgesics, and the like.
The copolymer has a number of properties which suit it to a variety of medical and dental applications. First, the copolymer is able to act as a thickener for increasing the viscosity of liquid forms of therapeutic agents, such as syrups, gels, and the like. Second, the copolymer is compatible with cationic materials, and thus may be used in oral care and medical compositions where cationic agents are used. For example, oral care compositions for plaque and tartar control often contain biocides. These are often cationic in nature and thus many conventional thickeners are incompatible with the biocide. Further, the anionic characters of the ampholytic polymer would be beneficial in inhibiting calcium phosphate build up and in inhibiting the enzymatic hydrolysis of pyrophosphate, a commonly used tartar control agent. The present copolymer is compatible with a variety of both cationic and anionic materials and thus has applicability as a thickener and carrier in such compositions. Thus, they can be used in various applications such as body implants, coatings for catheters, cannulae, antiperspirant and deodorant formulations, coating for medical devices, gloves, removable protective coatings, wound dressings, and the like.
Third, the copolymer has bioadhesive properties. By selecting the relative proportions of cationic and anionic groups in the copolymer, the copolymer can be tailored such that it adheres preferentially in a particular region of the gastro-intestinal system depending on the local pH. The bioadhesive properties of the copolymer are effective in a variety of drug delivery systems, including tablets, pills, syrups, and the like. For example, when used in tablets, the copolymer assists the tablet in adhering to the membrane of the chosen site in the digestive system so that, as the pill swells, the drug is released in high concentration at the selected site of absorption.
Fourth, the copolymer has properties as an absorption or penetration enhancer. While not fully understood, it is believed that paracellular transport of drugs is facilitated by the copolymer. It is likely that the copolymer assists in opening the tight junction between epithelial cells so that the drug may pass therethrough.
Fifth, the copolymer is capable of acting as an ion binding agent. For example, the copolymer effectively binds phosphates in the blood stream over a wide range of pH. The copolymer may thus be used in the treatment of hyperphosphatemia.
Clearly, many applications can take advantage of two or more of the properties of the copolymer. For example, in the case of phosphate binding, the ability of the copolymer to act as an absorption enhancer allows the copolymer to be used in oral compositions.
In another embodiment, the copolymer is used in the oral delivery of insulin and other proteins and peptides to the blood stream from the gastrointestinal system. First, the copolymer is compatible with insulin and other proteins and peptides. The anionic portions of the copolymer act to keep the insulin in solution at low pH. Second, the bioadhesion properties of the copolymer act to concentrate the insulin adjacent to the membrane of the intestinal tract where it can transported into the blood stream. Third, the penetration enhancing characteristics of the copolymer facilitate this transport process. To protect the insulin from degradation in the stomach and intestinal tract by trypsin and chymotrypsin, compositions containing the copolymer and insulin preferably also include an enzyme inhibitor. Optionally, the enzyme inhibitor is chemically attached to the copolymer. As with other drug delivery systems, the insulin/copolymer system may be used in the form of tablets, pills, capsules, suspensions, syrups, and the like.
In general, therefore, the copolymers of this invention can be used in a host of applications where the presence of acidic and basic groups in the same molecule is a useful property.
While not intended to limit the invention, the following examples are illustrative of the methods of preparing the copolymers of the present invention, their properties, and formulations in which they can be used. Throughout, viscosities were measured using a Brookfield Viscometer with RV spindles. All viscosities were measured at 20 rpm.